Makiko Kan

Numerical Study of the Formation of Transverse Dunes and Linear Dunes

Transverse dunes and linear dunes are simulated numerically in order to make clear the mechanism of the formation of two kinds of typical sand dunes. The numerical method employed in this study can be divided into three parts: (i) Calculation of the air flow above the sand dunes; (ii) Estimation of the sand transfer caused by the flow through the friction; (iii) Determination of the shape of the sand ground. Since the computational area has been changed due to the last step, these procedures are repeated until typical shapes of the sand dunes are formed. One kind of the simulated dunes, which is formed by one wind direction, becomes essentially parallel straight ridges at right angle to the wind direction with only one slip-face on the lee side, which is known as the transverse dunes; The other one, which is formed by two directional wind, becomes essentially parallel straight ridge at the converging direction with two slip-faces on both sides, which is known as linear dunes.

Numerical Simulation of Formation and Movement of Various Sand Dunes

In this paper, four types of sand dunes are simulated by using Large-Eddy Simulation (LES) method. In the flow direction and span direction cyclic boundary conditions are imposed for velocity and pressure. The movement of the sand dunes which are well know as barchan dunes, transverse dunes, linear dunes and Chinese wall have been investigated. The numerical method employed in this study can be divided into three parts: (i) calculation of the air flow above the sand dunes using standard MAC method with a generalized coordinate system, (ii) estimation of the sand transfer caused by the flow through the friction, (iii) determination of the shape of the ground. Because the computational area has been changed due to step (iii), steps (i)–(iii) are repeated until prescribed times.